Editorial

The theory of complex systems generates new models in which, for example, we observe some phase transitions (such as the transition from cooperative behavior to a non-cooperative one), and we try to identify the critical parameters of these transitions. We can use system dynamics approaches to model, to simulate and to understand the complex dynamics of socio-technical systems. The relevancy of these new approaches and ways of modelling is based on the fact that economic and social scientists now have to study evolving systems. We have to learn how to understand, how to observe and how to measure systems (micro or macro) in which structures, global behaviors and internal relations are changing. Analytically, their relevancy comes from the multiplicity of solutions or of equilibria in some non linear dynamics analysis and from the fact that we can get some solutions with cycles or chaotic behaviour. However, the domain of the EJESS is not restricted to modelling or methodological approaches of dynamic evolving process in economic and social systems. In short, we must pay attention to the new economy, from a critical as well as from a positive point of view.